The invention concerns a process for evaluating the dynamic request of a driver for the driving strategy of an automatic or automated transmission of a motor vehicle.
A driving strategy for automatic or automated transmissions of motor vehicles, in particular continuously variable and stepped automatic mechanical transmissions and automated transmissions, have among others the function of setting the correct ratio or the correct rotational speed of the engine for the driver. The driving strategy reacts here especially to the driver who steers, brakes and gives gas. The driver here dynamic articulates his wish for driving essentially via the accelerator pedal (xe2x80x9cgas pedalxe2x80x9d), that is, via the absolute accelerator pedal position and by the manner in which he opens the throttle or closes the throttle.
The accelerator pedal gradient or a similar signal directly coupled therewith has been customarily used in the prior art to judge how the driver moves the accelerator pedal. The accelerator pedal gradient is here the first inference in time of the usually filtered accelerator pedal position or the filtered first inference in time of the unfiltered signal of the accelerator pedal position. The use of said parameter of accelerator pedal gradient for the driving strategy has some fundamental disadvantages.
On one hand, it is very difficult and in all probability also not implementable to differentiate at substitute programming and application expense between a very slow continuous change of the accelerator pedal position by the driver, that is, a very small driving activity, and the usually existing permanent small interferences (so-called xe2x80x9cjittersxe2x80x9d) on the measured signal of the accelerator pedal position. The driving strategy thus can react very poorly, or not at all, to very slow accelerator pedal movements of the driver.
Besides, the accelerator pedal gradient itself does not take into account the absolute change of the accelerator pedal position, or only indirectly does, but only the speed at which said change occurs. But the driver expects upon certain accelerator pedal movement with a slight change of the accelerator pedal value a reaction of the vehicle different from that upon an equally quick accelerator pedal movement with a greater change of the accelerator pedal value. In addition, the level of accelerator pedal value, starting from which he introduces said change, is relevant to the driver""s expectation. Since these different activities of the driver cannot be differentiated by the accelerator pedal gradient and yet have to be taken into account in the driving strategy, at least one other or a different input signal is required for the driving strategy.
The accelerator pedal gradient also reproduces the driver""s request for dynamics only very incompletely. Determined by principle, the gradient immediately breaks down again after the end of the accelerator pedal movement. However, the driver""s request for a dynamic reaction of the vehicle stays longer or only breaks down slowly instead of promptly. If nevertheless now the driver""s request for dynamics is adequately reflected by means of the accelerator pedal gradient, an expensive processing of said operand related to the past is further needed.
Due to the accelerator pedal geometry and the accelerator pedal spring tension (supplying and restoring forces), the accelerator pedal gradient that the driver can adjust and obtain depends on the direction of movement of the accelerator pedal (open throttle, close throttle) and on the position of the accelerator pedal at the start of the accelerator pedal movement. For example, during a subjectively xe2x80x9cequally quickxe2x80x9d accelerator pedal change, the driver adjusts from an absolute accelerator pedal position of 0% an accelerator pedal gradient different from an accelerator pedal position of 50% also determined by the kinematics of the accelerator pedal and the foot actuation.
If the driver changes the direction of movement of the accelerator pedal, a divergence between the calculated and the actual accelerator pedal gradient, a so-called caster of the accelerator pedal gradient results, especially due to filtering time. This is disturbing for the driver especially at the reversal point of a quick change in the direction of movement of the accelerator pedal (quick positive or quick negative load change), since here within the caster time the actual and the calculated accelerator pedal gradients have different signs and the driving strategy logically xe2x80x9cwronglyxe2x80x9d reacts to this input signal in a manner unexpected by the driver.
Therefore, the problem on which this invention is based is to provide an input signal for the driving strategy of an automatic or automated transmission which correctly reflects, at low programming and application cost, the driver""s request for driving dynamics which he indicates by the movement of the accelerator pedal.
This problem is solved, by the process according to the invention, described in further detail below.
It is therefore proposed, according to the invention, that an accelerator pedal stroke is calculated from the movement of the accelerator pedal, instead of the accelerator pedal gradient, as an input parameter for the driving strategy of the transmission equivalent to the driving dynamic request. A rough value of the accelerator pedal stroke is defined here as an actual accelerator pedal position minus the accelerator pedal position at the beginning of the accelerator pedal movement. It is essential here that the rough value of the accelerator pedal stroke is determined from accelerator pedal values which are in a fixed event-dependent ratio to each other.
Compared to the prior art where to form the accelerator pedal gradient accelerator pedal values were always used which are in a fixed time ratio to each other, that is for example, the actual accelerator pedal value and the accelerator pedal value of the last calculated cycle, the change from a time-dependent ratio to an inventive event-dependent ration causes that the driver""s driving dynamic request to now be reflected as a parameter of the accelerator pedal movement instead of as a speed of change of the accelerator pedal position (xe2x80x9cmuch or little open throttlexe2x80x9d instead of xe2x80x9cquick or slow accelerator pedal movementxe2x80x9d).
According to the invention, the rough value of the accelerator pedal stroke is now event-dependently filtered to form the input parameter of the driving strategy so that a function for filtering the rough value of the accelerator pedal accelerator pedal position is at least approximately constant over a certain time, and the rough value of the accelerator pedal stroke existing at this moment breaks down over a presettable time function. By this breakdown, via the time function, is a xe2x80x9cforgetting effectxe2x80x9d which optimally simulates the driver""s subjective request for abating driving dynamics is advantageously reflected here. During, proper accelerator pedal movement the rough value of the accelerator pedal stroke is broken down to the accelerator pedal stroke.
According to the invention, an input signal is prepared for the driving strategy from the accelerator pedal stroke which signal rightly reflects the driver""s driving dynamic request which he indicates by movement of the accelerator pedal, specifically both for very quick and for very slow accelerator pedal movements, for ascending and for descending accelerator pedal movements regardless of the position of the accelerator pedal at the start of the accelerator pedal movement and of small interferences (so-called xe2x80x9cjittersxe2x80x9d) on the measured accelerator pedal position. The programming and application expenses are small here.
In a development of the invention, it is proposed to weigh periodically the rough value of the accelerator pedal stroke during the accelerator pedal movement until a moment at which the filtering function is started depending on events. It is proposed for the periodic weighing, according to the invention, to use the interval from beginning of the accelerator pedal movement until the actual moment of weighing or to design the periodic weighing as a time-discrete stepped function. In particular, it is advantageously possible hereby to take into account in addition a quick or slow opening or closing of throttle, for ex., to purposefully overcompensate the actual accelerator pedal movement without requiring a separate evaluation of the gradient of said accelerator pedal movement.
In other developments of the invention, it can be provided that prior to the start of the event-dependent filtering function, the rough value of the accelerator pedal stroke is weighed with a value of the accelerator pedal at the beginning of the accelerator pedal movement or with the value of the actual accelerator pedal position at the moment of the weighing. Thus, the driving strategy has available a relative accelerator pedal stroke as an input variable, instead of an absolute accelerator pedal stroke, which according to the subjective driver""s view corresponds to the desired driving dynamics especially in the case of accelerator pedal movements from a medium to a high accelerator pedal position.
During filtering, during periodic weighing and during value-related weighing, ascending and descending movements of the accelerator pedal, respectively, obviously can be treated differently with the start value of the accelerator pedal movement.
Obviously, it is also possible obviously to provide another control device instead of the accelerator pedal, or also in addition to the accelerator pedal, with an equivalent function with which the driver can act upon the power control of the driving device of the motor vehicle via an arbitrarily formed operative connection such as a manual lever or an electrically controllable driving speed regulator (xe2x80x9cTempomatxe2x80x9d) and to calculate the inventive accelerator pedal stroke from values of this control device.